Merge pull request #439 from MHM5000/master

Upgrading the Structure of files
Added Ruby and Perl section with come link and other links
une introduction aux makefile
Merge pull request #440 from OpenCode/patch-6

Added Ruby and Perl section with come link and other links
Merge pull request #442 from MHM5000/master

Knockout mix-up
Merge pull request #441 from maieul/master

une introduction aux makefile
Merge pull request #443 from MHM5000/master

Fixing and Adding various links
Gradle Section + Building and Testing with Gradle

Added a Gradle Section and the book Building and Testing with Gradle
Merge pull request #444 from randomducks/master

Gradle Section + Building and Testing with Gradle
README update
Formatting fixes:
Added empty line before heading "Information Retrieval" to fix html output.
Untabified one line in Python section.
remove broken macruby link
Merge pull request #445 from shelleyvadams/master

Formatting fixes:
Merge pull request #446 from eellson/remove-dead-link

remove broken macruby link
Initial removal of english books from chinese(zh) books list.
Removal decisions were made comparing it with the english(en) books list; itens with the exact same link were removed.
Further removal may need a more careful consideration, since for some reason these book's titles were translated to chinese in the *zh* list.
Added 3 chinese(zh) books.
Berkeley link doesn't require signup
Add french book "Calcul mathématique avec Sage", collectif
Merge pull request #450 from ericguirbal/fr

Add french book "Calcul mathématique avec Sage", collectif
Merge pull request #448 from hiisi13/master

Algorithms - Berkeley link doesn't require signup
Add Explore Flask book (crowdfunded)